Extreme Nature of Four Blue-excess Dust-obscured Galaxies Revealed by Optical Spectroscopy
Artikel i vetenskaplig tidskrift, 2022

We report optical spectroscopic observations of four blue-excess dust-obscured galaxies (BluDOGs) identified by the Subaru Hyper Suprime-Cam. BluDOGs are a subclass of dust-obscured galaxies (DOGs; defined with the extremely red color (i − [22])AB ≥ 7.0; Toba et al., showing a significant flux excess in the optical g and r bands over the power-law fits to the fluxes at the longer wavelengths. Noboriguchi et al. have suggested that BluDOGs may correspond to the blowing-out phase involved in a gas-rich major-merger scenario. However, the detailed properties of BluDOGs are not understood because of the lack of spectroscopic information. In this work, we carry out deep optical spectroscopic observations of four BluDOGs using Subaru/FOCAS and VLT/FORS2. The obtained spectra show broad emission lines with extremely large equivalent widths, and a blue wing in the C iv line profile. The redshifts are between 2.2 and 3.3. The averaged rest-frame equivalent widths of the C iv lines are 160 ± 33 Å, ∼7 times higher than the average of a typical type 1 quasar. The FWHMs of their velocity profiles are between 1990 and 4470 km s−1, and their asymmetric parameters are 0.05 and 0.25. Such strong C iv lines significantly affect the broadband magnitudes, which are partly the origin of the blue excess seen in the spectral energy distribution of BluDOGs. Their estimated supermassive black hole masses are 1.1 × 108 < M BH/M ⊙ <5.5 × 108. The inferred Eddington ratios of the BluDOGs are higher than 1 (1.1 < λ Edd < 3.8), suggesting that the BluDOGs are in a rapidly evolving phase of supermassive black holes.

Författare

Akatoki Noboriguchi

Ehime University

Shinshu University

Tohoku University

Tohru Nagao

Ehime University

Y. Toba

Academia Sinica

Kyoto University

Ehime University

National Astronomical Observatory of Japan

Kohei Ichikawa

Tohoku University

Masaru Kajisawa

Ehime University

Nanako Kato

Ehime University

Toshihiro Kawaguchi

Onomichi City University

Hideo Matsuhara

The Graduate University for Advanced Studies (SOKENDAI)

JAXA Institute of Space and Astronautical Science

Yoshiki Matsuoka

Ehime University

Kyoko Onishi

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Masafusa Onoue

Beijing University of Technology

Max-Planck-Gesellschaft

University of Tokyo

Nozomu Tamada

Ehime University

Koki Terao

National Astronomical Observatory of Japan

Tohoku University

Yuichi Terashima

Ehime University

Yoshihiro Ueda

Kyoto University

Takuji Yamashita

National Astronomical Observatory of Japan

Ehime University

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 941 2 195

Ämneskategorier

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik

Den kondenserade materiens fysik

DOI

10.3847/1538-4357/aca403

Mer information

Senast uppdaterat

2023-01-12